Bioluminescence is a chemical process by which some fish species can produce their own source of light. They have light producing organs known as photophores. The light is emitted from specialized cells called photocytes or from symbiotic fluorescent bacteria that are cultured by the fish in photophores. Most fish bioluminescence is blue (because blue-green light transmits … [Read more…]
An anadromous fish hatches and spawns in fresh water but spends most of its life in the salt water. This dual life cycle allows the younger fish to grow and feed in the less perilous fresh water habitats (fewer predators in the smaller systems) and the older, larger fish to grow and feed in the marine … [Read more…]
Electrofishing is a survey tool used to estimate species composition, fish abundance, and fish density in freshwater systems using an electrical current. An electroshocker creates a flow of current between an anode (i.e., ring on a backpack models) and cathode (i.e., rat tail on backpack models) that stuns fish that cross the electric field. Stunning … [Read more…]
Happy Halloween! Schreckstoff, German for “scary stuff,” is a chemical compound, glycosaminoglycan chondroitin, that some fish species release when they are injured. This “take-one -for-the-team” signal lets their conspecifics know that there is danger in the area. But more than just an alarm signal, Schreckstoff also serves as an immune response for the injured individual, warding off parasites and … [Read more…]
A meristic is a countable trait, such as number of gill rakers or number of dorsal fin spines. Morphometrics examines the size and shape using a measurable trait, such as standard length or wet weight, which can be gauged as a length, mass, angle or ratio of other measurements. Meristic traits and morphometrics are often used … [Read more…]
Habitat, is simply, the location where a fish lives. It applies to any and all life stages. It is where a fish survives, feeds, grows, and reproduces. The habitat of a fish depends on the species, from wetlands, to rivers, to coral reefs, to lakes, and more. Most fish do require well-oxygenated water. But, there … [Read more…]
In fisheries, recruitment refers to the number of fish surviving to enter a fishery. These fish have to pass through a number of life history stages (e.g., egg, larva, juvenile, etc.) before becoming vulnerable to fishing gear. Understanding recruitment dynamics is a very complex process – dependent upon the spawning stock biomass and environmental … [Read more…]
The terms overfishing and overfished are confusing because they address a similar subject. The difference between the two terms is subtle but significant. Overfishing refers to the current fishing rate which results in a higher harvest, or fishing mortality rate, than maximum sustainable yield (the maximum harvest level without negatively impacting the sustainability of the … [Read more…]
Teleosts are the most diverse group of fishes (over 26,500 extant species). Over half of all living vertebrate species are teleosts. Teleosts are characterized by a protrusible jaw (musculature gives them the ability to move their maxilla and premaxilla) and a symmetrical tail (their spine that ends at the caudal peduncle unlike, for example, sharks). Teleosts … [Read more…]
The caudal peduncle is the tapered region behind the dorsal and anal fins where the caudal fin attaches to the body. The depth of the caudal peduncle, which is measured at its narrowest point, gives some indication of the power of a fish and the speed at which it can swim. For example, ambush predators, … [Read more…]